1. Technical Field of the Invention
The present invention relates, generally, to a spool capsule for a sewing machine.
More particularly, the present invention relates to a spool capsule for a sewing machine for receiving a lower thread spool, having a concentrically disposed bore for mounting the spool capsule on a spool carrier pin, with a spring, serving as a locking device for axially retaining the spool capsule on the spool carrier pin, being inserted into a spool receiving space of the spool capsule. A section of the spring is constructed so that it is elastically displaceable radially, relative to the concentrically disposed bore, penetrating the bore in a manner analogous to a tendon.
2. Description of the Prior Art
With most conventional sewing machines designed for producing a so-called double-quilt stitch seam, the thread spool containing the lower thread supply is supported in a spool capsule. The spool capsule is rotatably supported on a central pin on a catcher or on a spool carrier, depending upon the construction of the catcher. A locking device on the spool capsule retains the latter on the pin of the catcher or spool carrier. The locking device, which is mounted on the bottom of the spool capsule, includes a plurality of movable components. A radially movable pawl engages an annular groove at the end of the pin, under the biassing pressure of a spring, and, in this manner, thereby secures the spool capsule against axial movement.
Such a conventional spool capsule is shown and described, e.g., in U.S. Pat. No. 3,232,258. A locking device on a spool capsule, with a radially movable pawl, is disclosed in Switzerland Patent No. 395,711. In Switzerland Patent No. 569,822, the locking device consists of a pawl, as well, which is displaceable vertically to the central axis of the pin of the spool carrier beyond the center point of the spool capsule.
Such conventional spool capsules, or locking devices, serve their purposes in an adequate manner. However, such prior art devices have the drawback that their manufacture requires an extremely high expenditure resulting from the need to manufacture a plurality of components which, furthermore, have to be produced with high precision. Moreover, a mounting of the locking device is complicated because the individual components are very small and their assembly and adjustment is, consequently, highly labor-intensive. An additional drawback is that the locking device requires much space and, accordingly, unnecessarily limits, in the spool capsule, the space available for the lower thread supply, i.e., for the lower thread spool.